In this case, you should set either the object properties or the layer properties to use a True Colour. These are different from the index colours in that .ctb files ignore them and they always print true to colour.
Say that I want to have a line on my drawing print in a colour AND be 0.70 mm. I would set up the layer so it has a True Color and adjust the lineweight, too. Then, that layer would print in the specified True Color at .70 mm thick. Yes?
Also, do the Color Books work like True Color, in that they will override the Land F/X line colours?
The width of the concept line won't follow typical ctb plotting widths. Instead, it will set the width based on the actual 1:1 scale size in your plan. The intent is to make something like a 6" or 0.15m curb width, or a 2'/0.6m wall width.
Yes, colour books work like true colour. They will override the ctb settings and will always print true to colour.
There are two ways to change thickness of a polyline in CAD:
Select the polyline, open the properties palette, and change "Global width". This is tied to 1:1 scale too, as with what I mentioned above.
In properties, or in Layer settings, change the set Lineweight. This can be tied to your end plot 0.7mm weight you were talking about. Make sure you check "Plot Object Lineweights" in your plot options for this to actually plot through to your PDF/plotter.